Researchers are currently hindered from observing dynamic liquid-liquid and liquid-solid interactions in transmission electron microscopes (TEMs) and scanning transmission electron microscopes (STEMs). Yet, solid-state materials and fluids interact in many important ways. For example, solid-state nanoparticles are formed via solution-based synthesis, and biological cells exist live only in a fluid environment. This project will develop a method for imaging these events at nanometer scale resolutions in continuously flowing fluids using STEM. Phase I designed and constructed an experimental apparatus that allows both solid state and biological materials to be enclosed within microfluidic cells and imaged within the confined space of the STEM objective lens. This apparatus was tested with a range of materials and liquids. In Phase II, additional functions ¿ electrical biasing, heating/cooling, and controlled multi-fluid introduction ¿ will be incorporated to produce a new commercial grade product. Commercial Applications and other Benefits as described by the awardee: The real-time nanoscale interrogation of liquid-liquid and solid-liquid interactions should greatly improve the understanding of phenomena important to energy systems, including (1) electrochemical reactions that occur in batteries, fuel cells, and other energy generation systems, and (2) biologic systems that have significant application to bio-fuel formation